If I'm not mistaken, it actually puts a little more air and fuel in the chambers. For example on the older cars if you remember had a choke on the carb. When the motor was cool it would start with the choke open and the car would idle a little higher until it warmed up. This is the same idea without the high idle if I've read correctly. Yes, it is tricking the computer into thinking the incoming air is cooler than it really is. I'm sure someone will correct me if I'm wrong, but I believe that's how it works.

 

With a 4.7k resistor on the IAT it does detect the incoming air as approx 22* less than what the air temp really is.

Without variable valve timing (VVT) you cannot force more air into the chamber. So the only thing you can change are fuel trims and cwboyjohnny24 is right, you get more added fuel but only at WOT because that is when the PCM does not monitor AFR (I.E. open loop)

 

I've got enough resisters to make like 2 or 3 if someone else needs one let me know.